JP2023081465A - Magnet filter formed of iron-chrome-cobalt based magnet and production method thereof - Google Patents

Abstract

To provide a three-dimensional magnet filter which has strong attraction force to inside of a filter, and has a high freedom degree of a shape of capable of freely designing a size of the whole filter and an aperture of the filter according to a magnetic impurity which is desired to be removed.SOLUTION: There is provided a magnet filter comprising a three-dimensional lattice structure formed of an iron-chrome-cobalt based magnet.SELECTED DRAWING: Figure 4

Description

TECHNICAL FIELD The present invention relates to a magnetic filter using iron-chromium-cobalt magnets and a method for manufacturing the same.

Magnetic materials are divided into hard magnetic materials and soft magnetic materials. Among them, hard magnetic materials refer to magnetic materials that have a large coercive force and are difficult to be demagnetized by an external magnetic field. Representative examples include permanent magnets such as ferrite magnets, NdFeB magnets, SmCo magnets, and metal magnets. . Among them, metal magnets are characterized by being suitable for mass production of relatively small articles and complicated shapes. Examples of metal magnets include magnets mainly composed of iron, chromium and cobalt (iron-chromium-cobalt magnets) and magnets mainly composed of iron, aluminum, nickel and cobalt (alnico magnets).

Compared to alnico magnets, iron-chromium-cobalt magnets have higher magnetic flux density and maximum energy product, so they have superior magnetic performance. In addition, like alnico magnets, iron-chromium-cobalt magnets have a small temperature coefficient of residual magnetic flux density, so they have excellent temperature stability. It has the advantage of being easy to apply. Iron-chromium-cobalt magnets are used in stepping motors, relays, torque limiters, magnetic sensors and the like.

Various filters using the magnetic force of permanent magnets have also been proposed. Patent Literature 1 describes a mesh filter attached near a permanent magnet. This filter is made of a soft magnetic material such as iron, and becomes magnetized when attached near a magnet. Magnetic impurities in the sewage adhere not only to the permanent magnets, but also to this filter. It is said that this filter is removable, and magnetic impurities can be recovered by treating the removed filter with acid. Furthermore, Patent Document 2 describes that contaminants in the fluid flowing through the filter can be attracted and trapped by placing bonded magnets in a lattice pattern (two-dimensional) inside the filter.

On the other hand, Patent Document 3 shows that an iron-chromium-cobalt-based alloy material is used to obtain an iron-chromium-cobalt-based laminated alloy that can contribute to reducing cracks and chips during processing by an additive manufacturing method. However, nothing is described about a specific three-dimensional structure, only by fabricating a two-dimensional structure and confirming good magnet structure and magnetic properties.

Japanese Patent Application Laid-Open No. 2002-102862 Japanese Patent Publication No. 2000-502284 JP 2021-42456 A

The filter described in Patent Document 1 has a configuration in which a mesh filter made of a soft magnetic material such as iron is magnetized by a permanent magnet, and magnetic impurities are adsorbed and removed by the magnetized filter. The further away you are from it, the weaker it becomes. In Patent Document 1, impurities are adsorbed by both the permanent magnet magnetizing the mesh filter and the mesh filter, and it is considered that the adsorption force of the mesh filter alone is not so large.
The filter described in Patent Document 2 forms a two-dimensional lattice with bonded magnets, but it is considered that the two-dimensional grid described in Patent Document 2 cannot be expected to remove many impurities. There are limits to the shape, size, and opening size of the lattice that can be formed with bond magnets. Impossible.

The present invention is intended to solve the above problems, and has a strong adsorption force even inside the filter, and the size of the entire filter and the opening of the filter can be freely designed according to the magnetic impurities to be removed. An object of the present invention is to provide a magnet filter with a high degree of three-dimensional structure.

The inventor studied a magnet filter in which magnetic impurities are attracted to the permanent magnet itself instead of magnetizing a soft magnetic material with a permanent magnet as in the magnet filter described in Patent Document 1, and found that an iron-chromium-cobalt magnet The present inventors have found that the above object can be achieved by fabricating a three-dimensional lattice structure according to the method and using it as a filter as it is.

The magnetic filter of the present invention is characterized by having a three-dimensional lattice structure of iron-chromium-cobalt magnets.

A filter device according to the present invention is characterized by incorporating the above-mentioned magnet filter.

The method for producing a magnetic filter using an iron-chromium-cobalt magnet having a three-dimensional lattice structure according to the present invention is characterized by using an additive manufacturing method.

In the method of manufacturing a magnetic filter using an iron-chromium-cobalt-based magnet having a three-dimensional lattice structure according to the present invention, a shaped body of an iron-chromium-cobalt-based alloy formed by an additive manufacturing method is subjected to solution treatment and heat treatment in a magnetic field. , is characterized by performing aging treatment.

According to the present invention, iron-chromium-cobalt has a high degree of freedom in shape, which has a strong adsorption force even inside the filter, and allows the size of the entire filter and the opening of the filter to be freely designed according to the magnetic impurities to be removed. It is possible to provide a magnetic filter with system magnets.

FIG. 3 is a two-dimensional representation of the three-dimensional CAD data used to fabricate the modeled body of the example, where (a) is a top view and (b) is a side view. 4 is a photograph of a modeled body produced in an example. FIG. 2 is a two-dimensional representation of the three-dimensional CAD data used to fabricate the modeled body of the example, where (a) is a side view and (b) is a top view and a detailed view of a unit cell. 4 is a photograph of a modeled body produced in an example.

The present invention uses iron-chromium-cobalt magnets (hereinafter referred to as "FCC magnets") as permanent magnet materials. In this specification, unless otherwise specified, FCC magnets include magnetized magnets that function as permanent magnets, non-magnetized magnets, and demagnetized magnets. The magnet filter of the present invention refers to a single FCC magnet having a three-dimensional lattice structure, and includes magnetized, non-magnetized, and demagnetized magnets. Further, a device incorporating the magnet filter of the present invention is distinguished as a filter device from the magnet filter of the present invention, which is a single FCC magnet.

First, the FCC magnet will be described in detail. FCC magnets can be manufactured by melting a metallic material containing Fe, Cr and Co, solidifying by cooling, and then performing further heat treatment processes such as solution treatment, magnetic field heat treatment and aging treatment. These heat treatment steps cause spinodal decomposition in the Fe--Cr--Co alloy, and single domain fine grains of ferromagnetic phase are precipitated in the non-magnetic matrix. When spinodal decomposition occurs, magnetic anisotropy can be imparted to the Fe--Cr--Co alloy by applying a magnetic field in a specific direction. Hereinafter, the Fe--Cr--Co alloy before the heat treatment process is simply referred to as "FCC alloy" to distinguish it from "FCC magnet". Conventional FCC magnets are produced by casting or rolling methods. Details of the casting method and the rolling method are omitted in this specification.

The magnetic filter of the present invention can be produced by an additive manufacturing method (specifically sometimes called an additive manufacturing method). In additive manufacturing, unlike removal processing by cutting and molding processing in which material is poured into a mold and hardened, it is possible to easily and accurately create shapes that were once difficult to manufacture, such as mesh and porous shapes. can be manufactured. There are various methods of additive manufacturing, but for example, in the additive manufacturing method of the powder bed fusion method, powder material is spread over the entire modeling stage layer by layer, and lasers are applied to predetermined locations corresponding to 3D CAD data for each layer. , etc., to melt and solidify the powder material and integrate it. By repeating this process, a desired shaped body can be obtained. In the additive manufacturing method, not only resin but also metal can be used as the material. In Patent Document 3 and Japanese Patent Application No. 2021-019881, the applicant discloses a method of manufacturing an FCC alloy and an FCC magnet using a powder bed fusion type additive manufacturing method as a typical example.

The method of manufacturing FCC magnets by the additive manufacturing method will be described in detail below.

[Raw material powder]
In the present invention, a powdery FCC alloy is used as a raw material. More specifically, it is an FCC alloy composed of 17 to 45% Cr, 3 to 35% Co, and 5% or less additive elements in mass ratio, and the balance is Fe and inevitable impurities. The additive elements are, for example, Ti, Mo , V, Si, and Al. The additive element preferably contains at least Ti. For example, the mass ratio may be 17 to 45% Cr, 3 to 35% Co, 0.1 to 5% Ti, and the balance may be composed of Fe and unavoidable impurities. More preferably, the composition consists of 20 to 40% Cr, 5 to 14% Co, 0.1 to 0.6% Ti, and the balance being Fe and unavoidable impurities. It is also possible to contain elements other than Ti in a composite manner. A crucible is charged with a raw material obtained by weighing and mixing a predetermined amount of feed materials of each element so as to obtain an FCC alloy with the desired composition, high-frequency melting is performed, and the molten alloy is dropped from a nozzle under the crucible, and is subjected to high pressure. A gas atomized powder is produced by atomizing with argon. The FCC alloy powder obtained by classifying this gas-atomized powder is used as the raw material powder for the additive manufacturing method.

[Additive manufacturing]
To produce an FCC alloy shaped body, first, three-dimensional CAD data is created by dividing the shaped body into layers. Next, using a powder bed fusion type additive manufacturing machine, the raw material powder supplied to the base plate for each divided layer is melted at high speed by laser irradiation, rapidly cooled and solidified, and layered to create a 3D model on the base plate Create a body. Finally, the FCC alloy shaped body is obtained by separating the shaped body from the base plate.

Here, the conditions for layered manufacturing are appropriately determined in consideration of the particle size and composition of the raw material powder, the size, shape, characteristics of the molded body, production efficiency, and the like. Regarding the FCC alloy of the present invention, if the energy density (energy density of the heat source: J/mm ³ ) applied by laser irradiation for high-speed melting of the raw material powder is too small, the magnetic properties, particularly the squareness ratio, may deteriorate. The defect rate increases, making it difficult to put it to practical use as an FCC magnet. On the other hand, if the energy density is too high, the raw material powder will melt over a wide area around the laser irradiation position, making it difficult to maintain the shape of the modeled body. From these viewpoints, the energy density (J/mm ³ ) is preferably 35 or more, more preferably 35 or more and 130 or less, still more preferably 50 or more and 110 or less, and more than 60 and 95 or less. More preferred. Furthermore, in order to achieve such an energy density, it is preferable to set the thickness of one layer of the raw material powder layer to 10 to 80 μm during lamination molding. It is preferable that the irradiation beam diameter of the laser is about 0.1 mm. The laser output is preferably 50-400W. The laser scanning speed is preferably 400-2500 mm/s. The laser scanning pitch is preferably 0.04 to 0.15 mm. Here, the energy density E (J/mm ³ ) is the laser output P (W), the laser scanning speed v (mm/s), the laser scanning pitch a (mm), and the raw material powder layer thickness d (mm). It is obtained from the formula (1) using

E=P/(v×a×d) (1)

[Modeled body]
Next, the three-dimensional lattice structure forming the magnet filter will be described. The three-dimensional lattice structure in the present invention is a structure having a plurality of internal voids communicating with the outside, and may be of any configuration as long as it can be defined by three-dimensional CAD data. The internal voids may communicate with each other to form one or more voids. A typical example is a structure formed by repeating a framework (unit cell) that defines one open space in the front, back, left, right, up, down, and oblique directions, that is, in three-dimensional directions.

Examples include a cubic lattice with square openings shown in FIG. 1, a three-dimensional mesh lattice such as a polyhedral lattice called a Kelvin lattice shown in FIG. 2, a honeycomb structure, and other structures that define a plurality of internal voids. A unit cell does not necessarily have to be composed of a combination of straight lines, and may include curved lines. The thickness of the frame does not have to be constant. It may be configured by a combination of a plurality of types of unit cells. There may be differences in dimensions depending on the position. For example, the structure may be such that the space becomes wider toward the inside, or vice versa. The repetition regularity may be somewhat rough.

In the present invention, any lattice structure can be formed by creating three-dimensional CAD data. Therefore, it is possible to form a shaped body having any lattice structure according to the size of the magnetic impurities to be removed by the magnet filter, the viscosity of the liquid containing the magnetic impurities, and the like. Considering the strength of the shaped body and the ability to remove magnetic impurities, the thickness of the finest part of the lattice structure is preferably 0.2 mm or more. Also, the area of one opening is preferably 0.04 mm ^{2 or} more.

[Heat treatment]
After shaping, the shaped body is subjected to solution treatment, heat treatment in a magnetic field, and aging treatment.

The solution treatment is carried out in a vacuum or reduced pressure atmosphere, or an oxidizing atmosphere (typically in the air) at a temperature of 600° C. or higher and 950° C. or lower, preferably 700° C. or higher and 850° C. or lower. Maintain for no less than 20 minutes. By this solution treatment, the FCC alloy becomes a solid solution (α phase) of a ferromagnetic element and a nonmagnetic element.

In the magnetic field heat treatment, the temperature of the shaped body is maintained in a magnetic field of, for example, 200 kA/m or more in a range of 600° C. or more and 700° C. or less, preferably 620° C. or more and 660° C. or less, for example, for 60 minutes or more and 90 minutes or less. . By this heat treatment in a magnetic field, the FCC alloy undergoes spinodal decomposition and changes into a state of being separated into two phases, α1 phase (FeCo ferromagnetic phase) and α2 phase (Cr nonmagnetic phase). Since the magnetic field is applied when the spinodal decomposition proceeds, the ferromagnetic α1 phase grows long in alignment with the direction of the magnetic field. As a result, shape magnetic anisotropy can be developed. The atmosphere for the heat treatment in the magnetic field may be the air.

The aging treatment is performed in a temperature range of 400°C or higher and 670°C or lower. In the aging treatment, from the aging treatment start temperature (for example, 570 to 670°C) that is about 5 to 30°C lower than the temperature of the heat treatment in the magnetic field to the aging treatment end temperature (for example, 400 to 600°C), 1 to 7°C per hour, preferably It preferably includes a process of controlled cooling at a cooling rate of 2-6°C per hour. The temperature of the magnetic field heat treatment may be once lowered to below the aging treatment start temperature. In that case, the cooling is started after the temperature is raised to the aging treatment start temperature. As a result, the composition difference between the α1 phase and the α2 phase can be expanded, and the phase can be separated into a phase richer in FeCo and a phase richer in Cr, so that the α1 phase can be grown further in the direction of the magnetic field to increase the coercive force. be possible. The atmosphere for the aging treatment may also be the air.

[How to use the magnet filter]
In the magnet filter of the present invention, since the permanent magnet itself forms a filter shape, magnetic impurities are adsorbed by magnetizing the magnet filter itself, and the adsorbed magnetic impurities are demagnetized. Can be easily removed and recovered. Moreover, it is applicable to various usage patterns. For example, a magnetized filter is immersed in a tank containing magnetic impurities to be removed, and the magnetic filter with the magnetic impurities adsorbed is taken out of the tank and then demagnetized to easily remove the magnetic impurities in the tank. can be recovered. Alternatively, a magnet filter may be arranged in a device having a magnetization/demagnetization function, magnetized to flow liquid containing magnetic impurities, and then demagnetized to wash away adhering magnetic impurities.

[Filter device]
Furthermore, it is possible to provide a filter device incorporating the magnet filter of the present invention. Examples of the filter device include those in which the magnet filter of the present invention is arranged in a device having a demagnetization function by an electromagnet or the like, and those having a function of cleaning the magnet filter after demagnetization. The magnet filter does not necessarily need to be fixed in the device, and may be taken out as appropriate for demagnetization and cleaning.

Advantages of forming the magnetic filter of the present invention by the additive manufacturing method will be described below. First, it is extremely difficult to manufacture an FCC magnet having a three-dimensional lattice structure as in the present invention by the conventional methods of manufacturing FCC magnets, such as casting, rolling, and sintering. It is almost impossible to form a lattice structure by cutting a mass of cast alloy or sintered body. is required. According to the additive manufacturing method, such an FCC magnet alloy with a three-dimensional lattice structure, which has been very difficult to manufacture in the past, can be manufactured at a relatively low cost in a short period of time.

Further, since the magnet filter of the present invention uses the hard magnetic material itself as the magnet filter main body, it has a magnetomotive force even inside the three-dimensional lattice structure. In this regard, as in the filter described in Patent Document 1, compared to the case where a soft magnetic material such as iron is magnetized with a permanent magnet, it has a strong adsorption force even inside the filter, and has a high surface area and a high porosity. As a filter with a three-dimensional lattice structure that has a large contact area with a fluid containing impurities, it is expected that a magnetic filter with the highest adsorption force will be realized.

In addition, in the manufacturing process of FCC magnets by the additive manufacturing method, the FCC alloy is heat-treated at a high temperature after shaping to form an FCC magnet. Among them, it is a permanent magnet suitable for the additive manufacturing method.

Three-dimensional CAD data of a cubic lattice as shown in FIG. 1 was prepared. Fig. 1(a) is a top view of the three-dimensional CAD data of this cubic lattice expressed in two dimensions and a diagram showing the dimensions of the unit lattice, and (b) is a side view of the same cubic lattice and a diagram showing the dimensions of the unit lattice. be.

A predetermined amount of the feed material of each element is weighed so that the composition is mass%, 10.1% Co, 24.5% Cr, 0.2% Ti, 0.5% C, and the balance Fe. The mixed raw materials were charged into a crucible, subjected to high-frequency melting in vacuum, and the melted alloy was dropped from a nozzle with a diameter of 5 mm under the crucible and sprayed with high-pressure argon to prepare gas-atomized powder. This gas-atomized powder was classified to obtain FCC alloy powder of 10 to 60 μm. This was used as raw material powder.

Using a powder bed fusion type layered modeling machine (EOS-M290 manufactured by EOS), the raw material powder supplied on the S45C base plate was melted at high speed by laser irradiation and rapidly cooled and solidified to produce the modeled body shown in FIG. The dimensions of each part in FIG. 1 are as follows. X: 10 mm, Y: 10 mm, Z: 20 mm, dimensions of the opening (x1, y1, z1): 1.3 mm, thickness of the smallest part (x2, y2, z2): 0.6 mm, that is, size: 2000 mm ³ , 1 side (opening + magnet portion): about 1.9 mm, area of opening: 1.7 mm ² cubic lattice.
The additive manufacturing conditions were as follows.
・One layer thickness of raw material powder layer / 40 μm
・Laser beam diameter / about 0.1 mm
・Laser output/200W
・Laser scanning speed/800mm/s
・Scan pitch/0.09mm
・Energy density/69 J/mm ³

As the heat treatment of the shaped body, first, solution treatment was performed at 900° C. for 1.3 hours, then in a magnetic field of 260 kA/m at 620° C. for 2.5 hours, and further aging treatment was performed at 625° C. for 1.2 hours. . After that, it was cooled at about 5°C/min. Through such heat treatment, an FCC magnet shaped body was obtained. A photograph (perspective view) of the resulting shaped body is shown in FIG.

[Magnetic properties]
The evaluation of the magnetic properties of the shaped body was carried out using a BH tracer using a magnet piece separately prepared under the same conditions. Obtain the BH curve for each shaped body, and from the BH curve, residual magnetic flux density B _r 1.30 [T], coercive force H _cB 44.5 [kA / m], maximum energy product (BH) _max 42 .5 [kJ/m ³ ] and the squareness ratio was 73.5%.

[Use as a magnet filter]
The obtained modeled body was magnetized with a solenoid magnetizer to obtain a magnet filter with an FCC magnet. The modeled object is immersed in 2 L of water (water tank size is 307×232×111 mm ³ ) containing 126.48 g of iron powder with a size of about 1 to 2 μm. I took it out. Iron powder adhered to the removed magnet filter. By demagnetizing the magnetic filter with a pulse demagnetizer and washing away the iron powder, the adhering iron powder could be easily recovered. When the weight of the iron powder washed away was measured, it was 0.80 g, and it was found that 22.8% of the iron powder was removed from the liquid with respect to the unit weight of the magnet filter.

Three-dimensional CAD data of a polyhedral grid as shown in FIG. 3 was prepared. FIG. 3(a) is a two-dimensional representation of three-dimensional CAD data of a polyhedral lattice, and FIG. 3(b) is a top view of the same polyhedral lattice and a detailed view of a unit lattice.

Under the same conditions as in Example 1, the FCC magnet model in FIG. A hexagonal opening area of 3.72 mm ² and a square opening area of 0.56 mm ² ) were fabricated. A photograph (perspective view) of the resulting shaped body is shown in FIG. An experiment was conducted under the same conditions as in Example 1 using the obtained magnet filter using the FCC magnet, and it was found that 38.6% of the iron powder could be removed from the liquid.

Claims (4)

A magnetic filter with an iron-chromium-cobalt magnet that has a three-dimensional lattice structure. A filter device using the magnet filter according to claim 1 . A method for producing a magnetic filter using an iron-chromium-cobalt magnet having a three-dimensional lattice structure, characterized by using an additive manufacturing method. An iron-chromium-cobalt magnet with a three-dimensional lattice structure, characterized by subjecting an iron-chromium-cobalt alloy shaped body formed by an additive manufacturing method to solution treatment, heat treatment in a magnetic field, and aging treatment. A method for manufacturing a magnet filter by.

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